I am sorry but I could not find this in the Laws of The Game. My textbook mentions 11 players and 12 substitutes, but it is a very poor quality textbook with lots of errors, hence I turn to you fellows.
The question is simple:

How many football players enter at the start of the match?

PS: I know there are total 22 players on the field at the time of play, but, I also wish to ask how many of them sit out on the benches (as substitutes, or maybe for other reasons?)

The competition rules must state how many substitutes may be named,
from three to a maximum of twelve.

So, there can be maximum of 12 x 2 = 24 players on the bench, resulting in total of 24 + 22 = 46 players.

But as you can see, the exact number of players sitting on the bench is determined by the competition rules. In Premier League, La Liga and most other leagues playing under federations associated with UEFA, and also in UEFA Champions League, the number of players sitting on the bench is 7, resulting in a total of 11 x 2 + 7 x 2 = 36 players. However, on the international level, the number of players sitting on the bench is usually maximal, i.e 12, again resulting in total of 46 players.

No. Maximum number of players playing per team is 11, not 7. so total number of players will be 11x2 = 22. And the maximum number of players named as substitutes is 7 per team, so 14 total substitutes. So the total number of players from both the teams is 22+14 = 36. 22 will be on the field & 14 will be on the bench,
– niranjanNov 21 '17 at 7:50

@niranjan, which statement you are trying to correct? No one said that maximum number of players playing per team is 7. Could you please quote the part you don't agree with?
– gdrtNov 21 '17 at 11:52

Gaurang Tandon's comment was > From what I can infer, the minimum number of players playing per team is 7, hence the minimum number of players on the field is 7×2=14. Am I correct? – Gaurang Tandon And your reply to that is, > Yes, absolutely.
– niranjanNov 21 '17 at 12:06